GCS: keep browser buttons working regardless of session state

This is a workaround for the fact the modem doens't trigger
a correctly opened state. It also doesn't even start handshaking
by itself, so the session management never even fails.

In general it's useful to keep the browser buttons working for
debugging purposes even if a valid session hasn't been established.
Merge pull request #1275 from peabody124/browser_buttons_enabled

GCS: keep browser buttons working regardless of state